I'm currently in Colorado and visited the Florissant Fossil National Monument we saw huge fossilized redwood trees, that were 100metres high, 5 metres dia and 700 years old. Only the stumps remain today, they're huge. This is from 35+ million years ago.
The CO2 levels were twice what they are today so the vegetation was really lush.
Trees grew to 100m tall and so many insects thrived, its amazing what CO2 does to help with plant growth.
Really makes you wonder about the climate change crazies today worrying about CO2 levels. https://coloradoearthscience.blogspot.com/2010/12/florissants-sequoias-redwood-giants-of.html
